Do not remove MDISPS customdata layer when removing multires modifier

and there are still another multires modifiers in the stack.

Helps to prevent loosing sculpt data when you occasionally added another
multires and reomved it with "X" button.

1 files changed, 20 insertions, 9 deletions

diff --git a/source/blender/editors/object/object_modifier.c b/source/blender/editors/object/object_modifier.c
index ff1b693d0e1..6e2eb5e8adc 100644
--- a/source/blender/editors/object/object_modifier.c
+++ b/source/blender/editors/object/object_modifier.c
@@ -204,17 +204,28 @@ int ED_object_modifier_remove(ReportList *reports, Main *bmain, Scene *scene, Ob
 		ob->dt = OB_TEXTURE;
 	}
 	else if(md->type == eModifierType_Multires) {
+		int ok= 1;
 		Mesh *me= ob->data;
+		ModifierData *tmpmd;
 
-		if(me->edit_mesh) {
-			EditMesh *em= me->edit_mesh;
-			/* CustomData_external_remove is used here only to mark layer as non-external
-			   for further free-ing, so zero element count looks safer than em->totface */
-			CustomData_external_remove(&em->fdata, &me->id, CD_MDISPS, 0);
-			EM_free_data_layer(em, &em->fdata, CD_MDISPS);
-		} else {
-			CustomData_external_remove(&me->fdata, &me->id, CD_MDISPS, me->totface);
-			CustomData_free_layer_active(&me->fdata, CD_MDISPS, me->totface);
+		/* ensure MDISPS CustomData layer is't used by another multires modifiers */
+		for(tmpmd= ob->modifiers.first; tmpmd; tmpmd= tmpmd->next)
+			if(tmpmd!=md && tmpmd->type == eModifierType_Multires) {
+				ok= 0;
+				break;
+			}
+
+		if(ok) {
+			if(me->edit_mesh) {
+				EditMesh *em= me->edit_mesh;
+				/* CustomData_external_remove is used here only to mark layer as non-external
+				   for further free-ing, so zero element count looks safer than em->totface */
+				CustomData_external_remove(&em->fdata, &me->id, CD_MDISPS, 0);
+				EM_free_data_layer(em, &em->fdata, CD_MDISPS);
+			} else {
+				CustomData_external_remove(&me->fdata, &me->id, CD_MDISPS, me->totface);
+				CustomData_free_layer_active(&me->fdata, CD_MDISPS, me->totface);
+			}
 		}
 	}